The present invention is directed to video enhanced night vision goggles.
Conventional, direct view night vision goggles have been in widespread use for several decades. All variants of the currently fielded hardware are based on a common optical architecture. This architecture consists of an objective lens, an image intensifier tube, and an eyepiece lens. Functionally, the objective lens focuses an image of a low light level scene onto the intensifier input plane (the photocathode). The intensifier tube amplifies this faint image and presents the brighter image on its output surface. The eyepiece lens allows a human eye to view the amplified image. The classical arrangement of these components is coaxial, with the objective lens, the image tube and the eyepiece lens sharing a common optical axis. This produces what is effectively a unity power telescope that has the ability to intensify low light level scenes and make them visible to a human observer. This telescopic device is typically positioned forward of the user""s eye by various means. There are common variations of this basic optomechanical architecture in which various optical folding mirrors and beamsplitters may be introduced into the optical path for the purpose of changing the overall telescope package shape. All variations of this basic night vision goggle (NVG) architecture, however, share a common attribute. They provide an intensified image by allowing the user to view the output xe2x80x9cscreenxe2x80x9d of the intensifier tube through a magnifying eyepiece optical train. For this reason, the conventional NVG architecture is often referred to as a xe2x80x9cdirect viewxe2x80x9d system because the observer views the image intensifier screen directly.
The image intensifier tube is also used in image intensified video cameras for specialized applications. The two primary areas of use for these cameras have been for scientific research and for surveillance. The surveillance applications are in the civilian security and military areas. In most of the prior uses of image intensified video cameras the devices have been either in a fixed site (such as a pan and tilt surveillance pedestal) or on a vehicle that can provide adequate electrical power as well as mechanical support. For example, in military applications the devices have been located typically either in an aircraft or ground tactical vehicle.
While presently fielded night vision goggles are in general adequate for their intended tasks, they have a number of shortcomings that compromise the effectiveness of the user. A major disadvantage is that the size and weight of existing night vision goggles tends to limit the mobility of the observer. Thus, it is important for a soldier be able to move freely to engage in such activities as running, rolling, crawling, etc. while the night vision goggle continues to be deployed and functioning. Such activities are referred to by the military as Individual Movement Techniques (IMT).
The presently fielded night vision goggle is typically a single, integrated unit that is placed in front of a user""s eyes. Such placement is accomplished either by the user holding the device by hand or with the use of a head or helmet mounting scheme. Present night vision goggle head mounting is generally accomplished by either mounting the goggle to a helmet or by use of a strap/harness device that is worn on the user""s head. There are significant problems with both approaches. The helmet is designed to protect the user""s head from injury in tactical situations and does this, in part, by xe2x80x9cfloatingxe2x80x9d on the skull. This results in an extremely poor platform for any kind of viewing device. Many NVG optical systems are xe2x80x9cexit pupil formingxe2x80x9d systems. To view the image from such systems the exit pupil of the NVG must coincide with the user""s eye pupil. The helmet mounted systems often fail to provide full imagery to the user because normal movement such as walking or running causes the helmet, and the exit pupil, to move.
The strap/harness device mounting approach is an attempt to avoid the helmet platform and mount the vision device to the same platform as the users eyes. This alleviates the exit pupil to eye pupil alignment problem. It does create another problem, however, that also degrades the user""s effectiveness. The typical NVG may weigh 1-2 pounds and has a profile created by a coaxial lens train which extends far in front of the user""s eyes. Such device must be cantilevered securely in front of the viewers eyes, and the strap/harness device accomplishes this only when it is painfully tight on the users head. The resulting discomfort makes it difficult for users to accomplish their assigned tasks and duties.
Presently field night vision goggles have additional limitations. Thus, such devices are xe2x80x9cpersonal vision devicesxe2x80x9d, and in the same way as in a pair of binoculars, the image from current devices is provided only to the individual user and cannot be xe2x80x9cexportedxe2x80x9d or transmitted to other users. It is not easy or convenient to process the optically generated image provided by the direct view NVG.
Additionally, the presently field night vision goggle incorporates a simple automatic electronic scheme for maintaining image quality over light levels ranging from twilight to overcast starlight. There are scene lighting conditions, however, that compromise the image quality of the NVG and thus reduce the effectiveness of the user. Examples of such conditions include scenes with wide brightness dynamic range, and daylight scenes. The user must be able to operate effectively in these situations and has difficulty doing so with the images provided by present systems.
Present night vision systems provide either an intensified image of the visible and near infrared (NIR) spectrum or an image based on sensitivity to one of the infrared atmospheric windows. NVGs and image intensified cameras provide images by sensing the visible and NIR wavelengths. Thermal cameras provide imagery of the 3-5 micron and 8-12 micron bandpasses. It would be advantageous to integrate the imagery from both types of sensors.
It is thus an object of the present invention to provide a man portable night vision goggle device which permits a user more freedom of movement than prior art devices.
In accordance with an aspect of the invention, a night vision device is provided which comprises a head mount, an image intensified video camera secured to the head mount, and a display comprised of an electrically operated flat panel and an optical eyepiece, which is secured to the head mount in such position that when the head mount is worn by a user, both the flat panel display and the eyepiece are located forward of the user""s eyes.
Thus, unlike the prior art, which uses a direct view optical train having a relatively long profile, the present invention employs a video camera and display. Such components can be made lighter in weight than in the direct view configuration and the screen and optical eyepiece do not extend far in front of the viewer""s eyes. Thus, the user has better mobility while the device is deployed and can more comfortably engage in a fuller range of activities.